Cannot Telnet to port 25 from Vista

I cannot seem to connect to an external mailserver through port 25 from my
Windows Vista machine. The problem is also from a couple of VM's whih reside
on that same desktop.
I've checked the following things:
Turned of the Vista Firewall
I can connect to the same external mailserver from another machine on my
network
I do not have any Anti virus installed on the Vista machine
I can telnet to other ports (for example port 80) on that same mail server
from Vista

So in short. My ISP isn't blocking port 25
Anti virus is not blocking port 25
Telnet is working
The remote host is reachable from Vista